1 TITLE:
1
Acute effects of dynamic stretching exercise on power output during concentric 2
dynamic constant external resistance leg extension 3
BRIEF RUNNING HEAD:
4
Acute effects of dynamic stretching exercise on muscular performance 5
LABORATORY WHERE THE RESEARCH WAS CONDUCTED:
6
Laboratory of Human Performance and Fitness, Graduate School of Education, 7
Hokkaido University 8
AUTHORS:
9
Taichi Yamaguchi 1, 2, Kojiro Ishii 2, Masanori Yamanaka 3 and Kazunori Yasuda 4 10
1 Laboratory of Food Ecology and Sports Science, Department of Foods Distribution, 11
Faculty of Dairy Science, Rakuno Gakuen University, 582 Bunkyodai-Midorimachi, 12
Ebetsu, Hokkaido 069-8501, Japan 13
2 Laboratory of Human Performance and Fitness, Graduate School of Education, 14
Hokkaido University, Kita-11 Nishi-7, Kita-ku, Sapporo, 060-0811, Japan 15
3 Department of Physical Therapy, School of Medicine, Hokkaido University, Kita-12 16
Nishi-5, Kita-ku, Sapporo, 060-0812, Japan 17
4 Department of Sports Medicine and Joint Reconstruction Surgery, Graduate School of 18
Medicine, Hokkaido University, Kita-15 Nishi-7, Kita-ku, Sapporo, 060-8638, Japan 19
ADDRESS CORRESPONDENCE TO:
20
Taichi Yamaguchi 21
Laboratory of Food Ecology and Sports Science, Department of Foods Distribution, 22
Faculty of Dairy Science, Rakuno Gakuen University, 582 Bunkyodai-Midorimachi, 23
Ebetsu, Hokkaido 069-8501, Japan 24
Telephone & Fax: +81-11-388-4914, E-mail: [email protected] 25
2 ABSTRACT
1 2
The purpose of the present study was to clarify the acute effect of dynamic 3
stretching exercise on muscular performance during concentric dynamic constant 4
external resistance (DCER, formally called isotonic) muscle actions under various 5
loads. Concentric DCER leg extension power outputs were measured in twelve healthy 6
men students after two types of pre-treatment. The pre-treatments were 1) dynamic 7
stretching treatment including two types of dynamic stretching exercise of leg 8
extensors and the other two types of dynamic stretching exercise simulating the leg 9
extension motion (2 sets of 15 times each with 30 seconds rest periods between sets;
10
total duration: about 8 minutes), and 2) non-stretching treatment by resting for 8 11
minutes in a sitting position. Loads during measurement of the power output were set 12
to 5%, 30% and 60% of the maximum voluntary contractile (MVC) torque with 13
isometric leg extension in each subject. The power output after the dynamic stretching 14
treatment was significantly (P<0.05) greater than that after the non-stretching 15
treatment under each load (5%MVC: 468.4 ± 102.6 W vs. 430.1 ± 73.0 W; 30%MVC:
16
520.4 ± 108.5 W vs. 491.0 ± 93.0 W; 60%MVC: 487.1 ± 100.6 W vs. 450.8 ± 83.7 W).
17
The present study demonstrated that dynamic stretching routines, such as dynamic 18
stretching exercise of target muscle groups and dynamic stretching exercise simulating 19
the actual motion pattern, significantly improve power output with concentric DCER 20
3 muscle actions under various loads. These results suggested that dynamic stretching 1
routines in warm-up protocols enhance power performance, because common power 2
activities are carried out by DCER muscle actions under various loads.
3 4
KEYWORDS 5
6
stretch, warm-up, performance, torque, velocity, rate of torque 7
development (RTD) 8
9 10 11 12 13 14 15 16 17 18 19 20
4 INTRODUCTION
1 2
The main purposes of warm-up prior to sports activity are prevention of 3
sports related injury and enhancement of performance (2,3,31,36). Therefore, most 4
athletes and coaches need to select and perform optimal warm-up routines. General 5
warm-up consists of low intensity aerobic exercise (e.g., running, cycling) and 6
stretching exercises (2,3,31,36,39). It has been a common belief that stretching 7
exercises enhance sporting ability by improving muscular performance (i.e., muscular 8
strength and power output) (2,3,31,36,39). A widely used warm-up technique is static 9
stretching (36,39). However, recent studies have shown that static stretching decreases 10
muscular performance during isometric (4,5,15,20,24,28,34), isokinetic (10-12,22,26) 11
or dynamic constant external resistance (DCER, formerly called isotonic) (21,37) 12
muscle action, and explosive performances, i.e., sprint running time (14,25,32) and 13
vertical jump height (8,9,23,33,38,40). Some researchers, therefore, proposed that 14
static stretching should not be included in warm-ups (8,10,21,26,37).
15
As for stretching techniques other than static stretching, there are ballistic, 16
proprioceptive neuromuscular facilitation (PNF) and dynamic stretching techniques 17
(2,3,18,19,36). If some of these techniques produce positive effects on muscular 18
performance, they may be incorporated into warm-up protocols. However, previous 19
studies reported that ballistic and PNF stretching, as well as static stretching, reduced 20
5 muscular or explosive performance (7,22,27). For example, Nelson and Kokkonen (27) 1
demonstrated that ballistic stretching of leg extensors, leg flexors and plantar flexors 2
decreased one repetition maximums (1RMs) of leg extension and leg flexion.
3
Moreover, Marek et al. (22) reported that PNF stretching (contract relax method) on 4
leg extensors decreased peak torque and mean power output with isokinetic leg 5
extension at angular velocities of 60 and 300 deggsec-1. On the other hand, Yamaguchi 6
and Ishii (35) clarified that dynamic stretching exercises of leg muscle groups 7
improved DCER leg press power. Fletcher and Jones (14) and Faigenbaum et al. (13) 8
also reported that sprint and jump performances were enhanced by dynamic stretching 9
exercises of leg muscle groups. However, in those previous studies (13,14,35), only 10
the acute effect of dynamic stretching exercise on each subject’s body weight loaded 11
muscular or explosive performance was examined. Actual sporting activities are 12
performed under not only the load of body weight but various loads. In order to 13
recommend dynamic stretching as a suitable stretching exercise during warm-ups for 14
various sporting activities, previous findings (13,14,35) are insufficient. Therefore, the 15
acute effect of dynamic stretching exercise on muscular performance under various 16
loads needs to be examined.
17
Dynamic stretching exercise is method to increase dynamic flexibility in the 18
target muscle group by contracting the antagonist muscle group without bouncing (35), 19
and/or to improve dynamic flexibility related to actual sports motion by simulating the 20
6 motion (18,19). In addition, previous reviews (16,18,19) suggested that dynamic 1
stretching exercise might produce positive effects on muscular performance, including:
2
postactivation potentiation (6,28,29), or increase in muscular temperature (6).
3
Therefore, dynamic stretching exercise may improve muscular performance under 4
various loads.
5
The purpose of the present study was to examine whether dynamic stretching 6
exercise improves muscular performance with concentric DCER muscle actions, which 7
constitute common sports activities, under various loads.
8 9
METHODS 10
11
Approach to the Problem 12
Our hypothesis was that dynamic stretching exercise improves muscular 13
performance with concentric DCER muscle actions under various loads. In order to 14
determine the validity of our hypothesis, experiments consisting of three testing days 15
interspersed with 3-6 days of rest were performed. On day 1, each subject visited our 16
laboratory to receive instructions. Maximum voluntary contractile (MVC) torque with 17
isometric leg extension was assessed to determine each subject’s relative load while 18
measuring concentric DCER leg extension power output. In addition, preliminary trials 19
for measuring concentric DCER leg extension power output were performed. On day 2, 20
7 the concentric DCER leg extension power outputs were assessed after one of two types 1
of pre-treatment: 1) dynamic stretching treatment including dynamic stretching 2
exercises of leg extensors and dynamic stretching exercises simulating the leg 3
extension motion, and 2) non-stretching treatment by resting in a sitting position.
4
Pre-treatment on day 2 was determined at random for each subject. On day 3, power 5
output was also assessed after the other pre-treatments different from that on day 2.
6
Loads during assessment of power output were set at 5% (relatively light load), 30%
7
(moderate load) and 60% (relatively heavy load) of the MVC torque assessed on day 1 8
for each subject (37) (Figure 1). The peak power outputs during concentric DCER leg 9
extensions under three kinds of load were compared between the two pre-treatments of 10
dynamic stretching and non-stretching in order to examine the acute effects of dynamic 11
stretching exercise on power output with concentric DCER leg extensions under 12
various loads.
13 14
Subjects 15
Twelve healthy men students (mean ± standard deviation; age, 24.1 ± 2.3 yr;
16
height, 171.8 ± 7.2 cm; weight, 62.0 ± 8.1 kg) took part in the present study. All 17
subjects were free of injury in their lower extremities. They were recreationally active 18
men and participated in a variety of activities (baseball, cycling, swimming, volleyball, 19
etc.), but not involved in regular training when the present study started. All subjects 20
8 were informed of the protocol, purpose and risks of the present study, and informed 1
consent was obtained from all subjects. The protocol was approved by the ethics 2
committee in Graduate School of Education, Hokkaido University.
3 4
Pre-Treatments 5
In dynamic stretching treatment, the subjects performed four types of dynamic 6
stretching exercise in a standing position (16,19,35,36). Two stretched the right leg 7
extensors (Figure 2a, b), and the other two simulated the leg extension, which is 8
motion during actual power assessment (Figure 2c, d). The subjects performed each 9
stretching exercise 5 times, slowly at first in order to accurately perform the motion, 10
and then 10 times as quickly and powerfully as possible in synchrony with the rhythm 11
of a digital metronome at 30 beats/min, without bouncing (35). Prior to performing 12
each stretching exercise, we explained to the subjects the muscle groups which should 13
be contracted. Each stretching exercise consisted of two successive repetitions.
14
Between stretching repetitions and while changing stretching exercises, each subject 15
stood upright for a 30-second rest period. Total duration of the dynamic stretching 16
treatment was approximately 8 minutes. The order of stretching exercises is shown 17
below:
18
Buttock kick. The subject contracted his hamstrings and flexed his knee joint 19
so that his heel kicked his buttock (Figure 2a).
20
9 Leg extension posterior aspect of body. The subject lent forward and raised 1
his foot from the floor with his hip and knee lightly flexed. Then, the subject 2
contracted his hip extensors and extended his hip joint so that his leg was extended to 3
the posterior aspect of his body (Figure 2b).
4
Thigh up. The subject contracted his hip flexors with his knee flexed and 5
flexed his hip joint so that his thigh came up to his chest (Figure 2c).
6
Leg extension anterior aspect of body. The subject contracted his hip flexors 7
and flexed his hip joint, raising his thigh parallel to the ground with his knee joint 8
flexed at about 90 degrees. Then, the subject contracted his quadriceps with the height 9
of his thigh maintained and extended his knee joint so that his leg extended to the 10
anterior aspect of his body (Figure 2d).
11
In the non-stretching treatment, each subject rested in a sitting position for 8 12
minutes. Concentric DCER leg extension power outputs commenced assessment 13
within 5 minutes after pre-treatment. This was the interval allowed for the subject to 14
move to the power measurement system and for straps to be fastened.
15 16
Measurement of Maximum Voluntary Contractile Torque and Concentric 17
Dynamic Constant External Resistance Leg Extension Power Outputs 18
The MVC torque and concentric DCER leg extension power output were 19
assessed using a power measurement system (37) based on a commercially available 20
10 machine, Power Processor (Vine Co., Ltd., Tokyo, Japan). Variable data were stored 1
on a personal computer at a sampling frequency of 500 Hz and calculated with a 2
commercially designed software program (VPM21, Vine). Starting positions in all 3
assessments were as follows. The subject sat on the seat of the measurement system 4
with the hip joint angle at about 90 degrees. The trunk, pelvis and thighs were firmly 5
fastened by strap belts. The wire of the measurement system was attached to the 6
subject’s right ankle with a strap, and wire length was adjusted so that the knee joint 7
angle was 90 degrees. Subjects were instructed to cross the arms in front of the chest 8
and not to shout during measurement.
9
Measurement of the maximum voluntary contractile torque. The wire length 10
of the measurement system was fixed at the starting position during the MVC torque 11
measurement (37). The subject was instructed to extend the right knee joint with 12
maximum effort for five seconds. The peak tension over five seconds was taken as the 13
MVC torque. This was measured two times with a rest period of 2 minutes. The higher 14
torque value of the two trials was taken as the variable MVC torque data for each 15
subject.
16
Measurement of the concentric dynamic constant external resistance leg 17
extension power output. The load of the measurement system wire was set to 5%, 30%
18
or 60% of the MVC torque measured on day 1 in each subject (37). Power outputs 19
were measured in the order of 5%MVC, 30%MVC and 60%MVC after each treatment 20
11 in all subjects. Each subject was instructed to pull the wire of the measurement system 1
by extending the right leg as quickly and powerfully as possible from the starting 2
position. Power output under each load was measured two times with a rest period of 2 3
minutes. Each subject also rested for 2 minutes while the load was changed. Peak 4
power output was recorded as the peak value in the power-time curve as assessed by 5
the Power Processor. The higher peak power output of the two measurements was 6
taken as the variable peak power output data (PP) under each load in each subject. In 7
order to investigate the mechanism of PP change after dynamic stretching exercises, 8
the tension (torque at peak power output: TPP), TPP/MVC torque (measured on day 1) 9
ratio (%MVC at peak power output: %MVCPP) and velocity (velocity at peak power 10
output: VPP) at peak power output, and the time from initial rise of power output to 11
peak power output (time to peak power output: TPP) were analyzed. Furthermore, the 12
peak tension (peak torque: PT), the time from 20% of peak torque to peak torque (time 13
to peak torque: TPT), the PT/TPT ratio (rate of torque development: RTD), and the 14
peak velocity (PV) during concentric DCER leg extension were also calculated. In 15
addition, intra-class correlation coefficients (R) for the test-retest of variable data 16
measured by the Power Processor ranged from 0.85 to 0.99, with no significant 17
differences between mean values for test vs. retest at either load (37).
18 19
12 Statistical Analyses
1
The paired t-test or Wilcoxon signed-rank test was utilized to examine the 2
differences between variable data under each load after the dynamic stretching and the 3
non-stretching treatments. Relationships between variable data were analyzed by 4
Pearson’s correlation coefficient. All variable data were expressed as the mean and 5
standard deviation, and the significance level was P ≤ 0.05.
6 7
RESULTS 8
9
Peak Power Output. The PP after the dynamic stretching treatment was 10
significantly (P<0.05) greater than that after the non-stretching treatment under each 11
load (Figure 3; 5%MVC: +8.9%; 30%MVC: +6.0%; 60%MVC: +8.1%).
12
Torque and Velocity at Peak Power Output. The results of comparisons in 13
the TPP and the VPP between both treatments differed under each load. As for the load 14
of 5%MVC, the TPP was significantly (P<0.05) greater (+6.5%) following the dynamic 15
stretching treatment compared with the non-stretching treatment. On the other hand, 16
the VPP after the dynamic stretching treatment tended to be higher (+2.0%) than after 17
the non-stretching treatment, but there was no significant difference (Table 1).
18
Moreover, the correlation coefficient (r) of the % change of TPP or VPP and the % 19
change of PP was 0.81 or 0.34, respectively, and only the relationship in the % 20
13 changes of TPP and PP was significantly (P<0.01) positively correlated (data not
1
shown).
2
As for the load of 30%MVC, TPP and VPP after the dynamic stretching 3
treatments tended to be greater than those after the non-stretching treatment (Table 1;
4
TPP: +3.0%; VPP: +2.8%), but these were not significant. In addition, there was no 5
significant correlation in the % change of TPP or VPP and the % change of PP (data not 6
shown; TPP: r=0.38; VPP: r=0.44).
7
As for the load of 60%MVC, both TPP and VPP were significantly (P<0.05) 8
greater after the dynamic stretching treatment compared with the non-stretching 9
treatment, although the % change in VPP (+5.0%) tended to be higher compared with 10
that in TPP (+3.2%)．Furthermore, only the relationship of the % change in VPP and PP 11
was significantly (P<0.01) positively correlated (data not shown; TPP: r=0.28; VPP: 12
r=0.83).
13
Time to Peak Power Output. There were no significant differences in mean 14
TPP between the dynamic stretching and the non-stretching treatments under all loads, 15
although in the load of 60%MVC, the TPP after the dynamic stretching treatment 16
tended to shown shorter than the non-stretching treatment (Table 1; -7.4%; P=0.08).
17
Peak Torque. There is no significant difference in mean PT between the 18
dynamic stretching and the non-stretching treatments, but TPT was significantly 19
(P<0.05) shorter with dynamic stretching treatment compared to the non-stretching 20
14 treatment under each load. RTD following the dynamic stretching treatment was
1
significantly (P<0.05) greater than that following the non-stretching treatment under 2
each load (Table 1).
3
Peak Velocity. PV after the dynamic stretching treatment was significantly 4
(P<0.05) higher than that after the non-stretching treatment under each load (Table 1).
5 6
DISCUSSION 7
8
The present study demonstrated that dynamic stretching routines, which 9
include dynamic stretching exercises of leg extensors and dynamic stretching exercises 10
simulating the leg extension motion, improve peak power outputs with concentric 11
DCER leg extensions under all three loads (relatively light load, moderate load and 12
relatively heavy load) (Figure 3), and that the time to peak torque is reduced and the 13
rate of torque development and peak velocity are increased after dynamic stretching 14
exercise under each loads (Table 1). On the other hand, the present study showed that 15
the tendency in changes of torque and velocity at peak power output differed under 16
each load (Table 1), suggesting that improvement in peak power output after dynamic 17
stretching exercise was load-specific.
18
In previous studies that investigated the acute effects of static, ballistic and 19
PNF stretching, almost all demonstrated the three techniques decreased muscular 20
15 performance (4,5,7-12,14,15,20-28,32-34,37,38). No studies, however, have revealed 1
that the three stretching techniques actually improved muscular performance. On the 2
other hand, regarding dynamic stretching, one study (35) clarified that dynamic 3
stretching exercises of leg muscle groups improved DCER leg press power output 4
under a load of each subject’s body weight. However, the acute effects of dynamic 5
stretching exercise on power output during DCER muscle actions under various loads 6
have not been clarified. The present study, therefore, examined the acute effects of 7
dynamic stretching exercises on power output during concentric DCER leg extensions 8
under a relatively light load (5%MVC), a moderate load (30%MVC) and a relatively 9
heavy load (60%MVC). The results of the present study demonstrated that dynamic 10
stretching exercises improved peak power outputs under all loads (Figure 3).
11
Furthermore, when the relationships between torque (%MVCPP) and power output (PP) 12
at peak power output following the dynamic stretching treatment and the 13
non-stretching treatment were depicted (Figure 4), the torque-power curve after 14
dynamic stretching exercise was consistently located above that after no stretching.
15
These facts suggest that dynamic stretching exercise improves power output with 16
concentric DCER muscle actions under various loads.
17
It is necessary to consider the reason why dynamic stretching exercises 18
improved concentric DCER leg extension power output. In the dynamic stretching 19
treatment, the motions simulating actual motions during assessment of power output 20
16 (i.e., leg extension) were included (Figure 2c and d). In addition, the subjects
1
performed dynamic stretching exercises 5 times, slowly at first in order to accurately 2
perform the motion, and then 10 times as quickly and powerfully as possible. Thus, it 3
is reasonable to assume that the subjects contracted their leg extensors, which are 4
agonist muscle groups in the leg extension motion, at maximum before assessment of 5
power output. After previous contractile activities, transient improvement in muscular 6
performance, that is, postactivation potentiation (PAP), occurs (29,30). The principal 7
mechanisms of PAP are considered to be phosphorylation of myosin regulatory light 8
chains, which renders the actin-myosin interaction more sensitive to Ca2+ released 9
from the sarcoplasmic reticulum. Increased sensitively to Ca2+ has greatest effect at 10
low myoplasmic levels of Ca2+, improving muscular performance. PAP shortens the 11
time to peak torque and increases the rate of torque development (30). The results of 12
the present study also demonstrated that dynamic stretching exercises shortened the 13
time to peak torque and increased the rate of torque development (Table 1). In addition, 14
Sale (30) suggested that PAP would shift the load (torque)-velocity relationship 15
upward and rightward. When the torque (%MVCPP) -velocity (VPP) relationships at 16
peak power output with concentric DCER leg extension after the dynamic stretching 17
treatment and the non-stretching treatment in the present study were depicted (Figure 18
5), the result supported the suggestion of Sale (30), that is, the torque-velocity 19
relationship after dynamic stretching exercises shifted upward and rightward.
20
17 Therefore, it was likely that PAP occurred after dynamic stretching exercises in the 1
present study.
2
The present result also showed that dynamic stretching exercises increased 3
peak velocity with concentric DCER leg extension under all loads (Table 1). This is 4
consistent with the finding of the previous study, which showed that dynamic 5
stretching exercises of lower muscle groups improved power output and increased the 6
peak velocity with DCER leg press (35; unpublished data about peak velocity). The 7
increase in peak velocity after dynamic stretching exercises may be attributed to the 8
high velocity muscle action involved in dynamic stretching exercises. This relatively 9
high velocity muscle action may increase contractile velocity in leg extensors and 10
improve the dynamic range of motion with leg extension (17), so peak leg extension 11
velocity would be increased after dynamic stretching exercises. Therefore, it is also 12
suggested that dynamic stretching exercises may improve peak velocity based on 13
velocity-specificity in the exercises.
14
In the present study, as for the load of 5%MVC, % increase in torque 15
(+6.5%) at peak power output after dynamic stretching exercises tended to be greater 16
than that in velocity (+2.0%), and only the relationship in % change of torque and peak 17
power output was significantly positively correlated. In contrast, as for the load of 18
60%MVC, % increase in velocity (+5.0%) at peak power output tended to be greater 19
than that in torque (+3.2%), and only the relationship in % change of velocity and peak 20
18 power output was significantly positively correlated. Regarding the load of
1
30%MVC, % increases in torque (+3.0%) and velocity (+2.8%) at peak power output 2
were similar. These results indicate that dynamic stretching exercise-induced 3
improvement of peak power output was due to the torque-related factor under the 4
relatively light load and the velocity-related factor under the relatively heavy load, and 5
that the factor shifted from torque-related to velocity-related as load increased. These 6
findings suggest that dynamic stretching exercise-induced improvement in peak power 7
output was load-specific.
8
It is unknown why dynamic stretching exercise-induced improvement in 9
peak power output was load-specific. Abbate et al. (1), however, showed that the 10
effects of PAP were dependent on the contractile velocity, i.e., increases in the force 11
and power output were found at high contractile velocities, whereas no effects were 12
detected at low contractile velocities. Naturally, the contractile velocity of leg 13
extensors during power assessment was relatively high at 5%MVC (relatively light 14
load), but relatively low at 60%MVC (relatively heavy load) in the present study. In 15
the light of the previous study (1), the effect of PAP may occur notably at 5%MVC.
16
On the other hand, the effect may not be induced at 60%MVC. Therefore, the increase 17
in torque at peak power output probably contributed to the improvement in peak power 18
output at 5%MVC. In contrast, as for the load of 60%MVC, since there was a 19
correlation between the increases in velocity at peak power output and the 20
19 improvement of peak power output, it is speculated that the dynamic stretching
1
exercise-induced positive effect on peak velocity contributed to improvement of peak 2
power output.
3
A previous study (37) investigated the acute effects of static stretching of leg 4
extensors on concentric DCER leg extension power outputs under the loads of 5
5%MVC, 30%MVC and 60%MVC, as in the present study. The previous results 6
demonstrated that static stretching reduced peak power outputs under all loads, in 7
contrast with the present study. In addition, the previous study indicated that the 8
velocity at peak power output was decreased following static stretching under each 9
load. On the other hand, the torque at peak power output was not changed. Thus, the 10
previous results suggested that the factor of static stretching-induced reduction in peak 11
power output was velocity-related and not load-specific. Furthermore, the previous 12
study revealed that the velocity at peak power output decreased after static stretching, 13
although the time to peak power output was not prolonged, suggesting that the knee 14
joint angle at peak power output was in a more flexed position; in other words, peak 15
power output occurred with elongating leg extensors. The present study indicated that 16
dynamic stretching exercises did not alter the velocities at peak power output at 17
5%MVC and 30%MVC (Table 1). On the other hand, at 60%MVC, the velocity at 18
peak power output was increased, although the time to peak power output tended to be 19
shortened (Table 1). It is thus speculated that the knee joint angle at peak power output 20
20 was not changed after dynamic stretching exercises. Consequently, it is likely that 1
there are differences between the factors of static stretching-induced reduction and 2
dynamic stretching exercise-induced improvement in peak power outputs.
3 4
PRACTICAL APPLICATIONS 5
6
The present study demonstrated that dynamic stretching routines, which 7
include dynamic stretching exercises of leg extensors and dynamic stretching exercises 8
simulating leg extension motion, improved concentric DCER leg extension power 9
under various loads. Common power activities consist of concentric DCER muscle 10
actions. Therefore, the results of the present study suggest that dynamic stretching 11
exercise enhances various power performances, and so that dynamic stretching 12
exercise in warm-up protocols may be more effective. Indeed, previous studies 13
reported that warm-up protocols including dynamic stretching exercises improved 14
jumping [vertical and long jumps (13)] and sprinting [20-m sprint (14) and shuttle run 15
(13)] performance. It is likely that dynamic stretching exercise enhances other 16
explosive performances (e.g., throwing, kicking, etc.). Future studies are needed to 17
investigate the relationship between the methods (e.g., exercise selection, repetition, 18
rest period) of dynamic stretching exercise and changes in muscular performance, and 19
to examine the acute effect of dynamic stretching exercise on muscular performance 20
21 with eccentric or eccentric-concentric (plyometric) DCER muscle actions under
1
various loads, in order to propose a suitable dynamic stretching routine in warm-up 2
protocols prior to various sporting activities.
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
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8 9 10 11 12 13 14 15 16 17 18 19 20
28 FIGURE LEGENDS
1 2
Figure 1 3
A summary of experimental protocol. DCER = dynamic constant external 4
resistance.
5 6
Figure 2 7
The four types of dynamic stretching exercise in the dynamic stretching 8
treatment. a: buttock kick; b: leg extension to posterior aspect of body; c: thigh up; d:
9
leg extension to anterior aspect of body.
10 11
Figure 3 12
The mean (+ S. D.) peak power outputs (PP) during concentric dynamic 13
constant external resistance (DCER) leg extension under the loads of 5%MVC, 14
30%MVC and 60%MVC following the dynamic stretching treatment and the 15
non-stretching treatment. * (P<0.05); ** (P<0.01) indicates a significant difference 16
between the dynamic stretching and the non-stretching treatments under each load.
17 18
Figure 4 19
The torque (%MVC at peak power output: %MVCPP) –power (peak power 20
29 output: PP) relationships following the dynamic stretching and the non-stretching 1
treatments. Values are means and S. D.
2 3
Figure 5 4
The torque (%MVC at peak power output: %MVCPP) –velocity (velocity at 5
peak power output: VPP) relationships following the dynamic stretching and the 6
non-stretching treatments. Values are means 7
8 9 10 11 12 13 14 15 16 17 18 19 20
30 Figure 1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
31 Figure 2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
32 Figure 3
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
33 Figure 4
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
34 Figure 5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
35 Table 1
1
Mean (± S. D.) variable data under the loads of 5%MVC, 30%MVC and 2
60%MVC following the dynamic stretching and the non-stretching treatments.
3 4 5 6 7 8 9 10 11 12 13
TPP=torque at peak power; %MVCPP=%MVC at peak power; VPP=velocity at peak 14
power; TPP=time to peak power; PT=peak torque; TPT=time to peak torque;
15
RTD=rate of torque development; PV=peak velocity. * (P<0.05); ** (P<0.01) 16
indicates a significant difference between the dynamic stretching and the 17
non-stretching treatments under each load.
18
5%MVC 30%MVC 60%MVC TPP (N) Dynamic Stretching 178.3 ± 23.0 239.0 ± 26.2 342.2 ± 33.4
Non-Stretching 167.5 ± 17.6 232.0 ± 22.1 331.5 ± 35.2
%MVCPP (%) Dynamic Stretching 33.4 ± 4.6 44.7 ± 3.8 63.9 ± 3.7
Non-Stretching 31.4 ± 3.2 43.6 ± 5.2 61.9 ± 3.6
VPP (m!sec-1) Dynamic Stretching 2.61 ± 0.31 2.17 ± 0.30 1.43 ± 0.28 Non-Stretching 2.56 ± 0.24 2.11 ± 0.29 1.36 ± 0.21 TPP (sec) Dynamic Stretching 0.116 ± 0.015 0.145 ± 0.022 0.177 ± 0.026 Non-Stretching 0.120 ± 0.013 0.149 ± 0.019 0.191 ± 0.030 PT (N) Dynamic Stretching 206.2 ± 20.0 277.7 ± 19.7 380.5 ± 34.5 Non-Stretching 202.5 ± 24.4 268.8 ± 24.7 376.2 ± 37.7 TPT (sec) Dynamic Stretching 0.060 ± 0.027 0.089 ± 0.031 0.142 ± 0.038 Non-Stretching 0.075 ± 0.028 0.107 ± 0.026 0.173 ± 0.034 RTD (N!sec-1) Dynamic Stretching 3385.3 ± 1894.3 2899.2 ± 1459.8 2282.1 ± 614.0 Non-Stretching 2332.5 ± 807.9 2163.6 ± 776.4 1786.9 ± 347.0 PV (m!sec-1) Dynamic Stretching 3.23 ± 0.30 2.43 ± 0.30 1.45 ± 0.30 Non-Stretching 3.06 ± 0.25 2.34 ± 0.28 1.36 ± 0.21
* *
*
*
* *
*
*
**
*
** * **
**
